Quality control is extremely important in the nutritional industry. Manufacturers spend substantial amounts of money in attempts to insure that their packaged liquid food products have not been contaminated. In some instances, a contaminated or spoiled liquid food product can easily be detected. For example, if gas producing bacteria are introduced into a liquid food product, a container holding the product maybe deformed due to bloating. As another example, a spoiled liquid nutritional product packaged in glass or translucent plastic often permits visual inspection of the liquid food product. As used herein and in the claims, "liquid nutritional product" is understood to mean a food in a liquid state, and a "liquid state" is understood to mean a state of matter wherein the food is practically incompressible, maintains its volume while conforming to the shape of a container, and may evaporate from an open container. Examples of liquid nutritional products in which spoilage may be detected by the method of the present invention include infant formula, medical nutritional products, beverages, puddings, yogurts, jellies, soups, and fruit and vegetable juices.
In some cases, no gas is produced, and when the liquid nutritional product spoils it does not become visibly discolored. One such condition of spoilage is known in the food industry as a flat/sour. Spoilage may be caused either by (a) container damage which permits the introduction of bacteria or micro-organisms, or (b) the contamination may be caused by improper sterilization of the liquid food product. In a flat/sour, micro-organisms "burped" into the can after sterilization can cause the product to curdle.
An incubation procedure allows the stored liquid food product to sit, often for between 2 and 4 weeks, in order to permit the growth of bacteria or other micro-organisms if the product is contaminated. The incubation procedure is yet another way in which manufacturers attempt to insure the quality control of their liquid food products. However, if the liquid food product is packaged in either metal cans, or containers having a label which precludes the visual inspection of the liquid food product there are few, if any, effective non-destructive screening procedures to test for the presence of flat/sours.
This is not to say that testing for flat/sours in metal or labeled containers is impossible. Flat/sours can still often be detected by physically shaking and handling individual cans. However, such a method obviously is extremely slow, somewhat subjective, and commercially impractical. Therefore, the need exists for a method which can efficiently detect the presence of flat/sours without shaking individual cans, or opening them in a destructive testing method.
The apparatus and method of the present invention meet this need through the employment of an inclined conveyor to separate containers suspected of containing spoiled liquid food products from containers of unspoiled food. Means for separating solid materials using a conveyor or inclined surface are well known in the prior art. Examples of such prior art include Rinker, U.S. Pat. No. 738,699; Sutton, et al. U.S. Pat. No. 1,114,935; Payne, U.S. Pat. No. 1,283,284; Stutzman, U.S. Pat. No. 2,658,616; and Schmidt et al., U.S. Pat. No. 3,978,986.
Rinker, U.S. Pat. No. 738,699, discloses a grain separator comprising a moving inclined belt with a feeder which discharges seeds near one top corner, so that seeds rolling more or less slowly according to their shape will be discharged into various receivers. Seeds of a relatively spherical shape are discharged first, while those seeds which depart from the spherical form will roll more slowly down the inclined surface of the belt and be discharged into other containers. Rinker teaches a method of separating objects based upon the shape of an object, and not with regard to whether there is any spoilage.
Sutton et al., U.S. Pat. No. 1,114,935, discloses a process and apparatus for sizing or classifying comminuted solid materials, with this process being dependent on the volume or size of the individual objects. Once again, a moving belt is involved, with the belt being rough and undulating, and the separation has nothing to do with the detection of spoilage.
Payne, U.S. Pat. No. 1,283,284, discloses a method and apparatus for the grading or sizing of materials, with the method being based on the equilibrium of the various solid particles relative to the distance between the particle's center of gravity and its point of support on an inclined surface. As in Sutton et al., the method of Payne is dependent on the size of the various solid particles, and has nothing to do with the detection of spoilage.
Stutzman, U.S. Pat. No. 2,658,616, discloses a process for classifying solid iron shots of similar sizes. The Stutzman process classifies the iron shots based upon their shape, i.e. spherical or nearly spherical, all the way to tear drop shaped pellets, and detection of spoilage is not involved.
Finally, Schmidt, et al. U.S. Pat. No. 3,978,986, discloses a process and apparatus for separating aspherical particles from spherical particles. Once again, the separation of the solid product is based on shape, and the detection of spoilage is not involved.
None of the above discussed patents disclose or suggest the use of an inclined conveyor in the non-destructive testing of a liquid food product for spoilage.